Method and apparatus for acquiring control information in a wireless communication system

ABSTRACT

One embodiment of the present invention relates to a method for acquiring control information, comprising: a step of receiving a plurality of first sequential indexes associated with a resource region via which downlink control information is transmitted; a step of determining a plurality of second indexes from the plurality of first indexes; and a step of determining control channel elements in the order of the resource regions according to the plurality of second indexes, and performing blind decoding wherein the determination o the plurality of second indexes is dependent on a transmission mode and/or downlink control information.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the National Phase of PCT/KR2012/007748 filed on Sep. 26, 2012, which claims priority under 35 U.S.C. 119(e) to U.S. Provisional Application Nos. 61/539,991 filed on Sep. 28, 2011 and 61/541,096 filed on Sep. 30, 2011, all of which are hereby expressly incorporated by reference into the present application.

TECHNICAL FIELD

The present invention relates to a method and apparatus for acquiring downlink control information in a wireless communication system.

BACKGROUND ART

Wireless communication systems have been widely used to provide various kinds of communication services such as voice or data services. Generally, a wireless communication system is a multiple access system that can communicate with multiple users by sharing available system resources (bandwidth, transmission (Tx) power, and the like). A variety of multiple access systems can be used. For example, a Code Division Multiple Access (CDMA) system, a Frequency Division Multiple Access (FDMA) system, a Time Division Multiple Access (TDMA) system, an Orthogonal Frequency Division Multiple Access (OFDMA) system, a Single Carrier Frequency-Division Multiple Access (SC-FDMA) system, a Multi-Carrier Frequency Division Multiple Access (MC-FDMA) system, and the like.

DISCLOSURE Technical Problem

An object of the present invention is to provide a method and apparatus for transceiving control information, and more particularly to UE operations for acquiring downlink control information (DCI) when E-PDCCH is introduced.

It is to be understood that technical objects to be achieved by the present invention are not limited to the aforementioned technical objects and other technical objects which are not mentioned herein will be apparent from the following description to one of ordinary skill in the art to which the present invention pertains.

Technical Solution

The object of the present invention can be achieved by providing a method for acquiring control information by a user equipment (UE) in a wireless communication system including: receiving a plurality of first indexes which are contiguous associated with a resource region in which downlink control information (DCI) is transmitted; determining a plurality of second indexes from the plurality of first indexes; and determining a control channel element (CCE) in order of resource regions dependent upon the plurality of second indexes, and performing blind decoding, wherein the determination of the plurality of second indexes is dependent upon at least one of a transmission (Tx) mode and a downlink control information (DCI) format.

In a second technical aspect of the present invention, a user equipment (UE) device for use in a wireless communication system includes: a reception (Rx) module; and a processor, wherein the processor receives a plurality of first indexes which are contiguous associated with a resource region in which downlink control information (DCI) is transmitted, determines a plurality of second indexes from the plurality of first indexes, and determines a control channel element (CCE) in order of resource regions dependent upon the plurality of second indexes and performs blind decoding in the order of the resource regions, wherein the determination of the plurality of second indexes is dependent upon at least one of a transmission (Tx) mode and a downlink control information (DCI) format.

The first and second technical aspects may include all or some parts of the following items.

If the transmission (Tx) mode is associated with data transmission based on a plurality of layers, and if blind decoding of the resource region is for a fallback downlink control information (DCI) format, the second indexes may be achieved by rearrangement of the first indexes in a manner that resource regions respectively indicated by the first indexes are distributed on a frequency axis. The data transmission associated with the fallback downlink control information (DCI) format may be achieved by use of a demodulation reference signal (DMRS). The fallback downlink control information (DCI) format may be downlink control information (DCI) format 1A.

If the transmission (Tx) mode is associated with data transmission based on a plurality of layers, and if blind decoding for the resource region is for a downlink control information (DCI) format associated with data transmission based on a plurality of layers, the second indexes are identical to the first indexes. The data transmission based on plurality of layers may be achieved by use of a demodulation reference signal (DMRS).

If the transmission (Tx) mode is not associated with data transmission for which a demodulation reference signal (DMRS) and a plurality of layers are used, the second indexes may be achieved by rearrangement of the first indexes in a manner that the resource regions respectively indicated by the first indexes are distributed on a frequency axis, irrespective of the downlink control information (DCI) format. In this case, the downlink control information (DCI) format associated with the data transmission based on the plurality of layers is any one of DCI format 2B and DCI format 2C.

The downlink control information (DCI) may be UE-specific control information.

The resource region may not include a resource region indicated by a physical control format indicator channel (PCFICH).

The resource region indicated by each of the first indexes may correspond to one resource block (RB).

The resource region indicated by each of the first indexes may correspond to the number of resource elements (REs) contained in a control channel element (CCE).

Advantageous Effects

As is apparent from the above description, the embodiments of the present invention can efficiently perform blind decoding according to a transmission (Tx) mode and/or downlink control information (DCI) format when E-PDCCH is introduced.

It will be appreciated by persons skilled in the art that the effects that can be achieved with the present invention are not limited to what has been particularly described hereinabove and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings.

DESCRIPTION OF DRAWINGS

FIG. 1 exemplarily shows a downlink radio frame structure.

FIG. 2 exemplarily shows a resource grid of one downlink slot.

FIG. 3 exemplarily shows a downlink subframe structure.

FIG. 4 exemplarily shows an uplink subframe structure.

FIGS. 5 and 6 exemplarily show a resource element group (REG) serving as an allocation unit of a downlink control channel.

FIG. 7 is a conceptual diagram illustrating a Physical Control Format Indicator Channel (PCFICH) transmission scheme.

FIG. 8 shows the positions of a PCFICH and a Physical hybrid ARQ indicator Channel (PHICH).

FIG. 9 shows a downlink resource element position mapped to a PHICH group.

FIG. 10 is a conceptual diagram illustrating a search space at each aggregation level.

FIGS. 11 and 12 are conceptual diagrams illustrating a method for performing blind decoding according to the embodiments of the present invention.

FIG. 13 is a block diagram illustrating a BS (or eNB) device and a UE device according to the embodiments.

BEST MODE

The following embodiments are proposed by combining constituent components and characteristics of the present invention according to a predetermined format. The individual constituent components or characteristics should be considered optional factors on the condition that there is no additional remark. If required, the individual constituent components or characteristics may not be combined with other components or characteristics. Also, some constituent components and/or characteristics may be combined to implement the embodiments of the present invention. The order of operations to be disclosed in the embodiments of the present invention may be changed. Some components or characteristics of any embodiment may also be included in other embodiments, or may be replaced with those of the other embodiments as necessary.

The embodiments of the present invention are disclosed on the basis of a data communication relationship between a base station and a terminal. In this case, the base station is used as a terminal node of a network via which the base station can directly communicate with the terminal. Specific operations to be conducted by the base station in the present invention may also be conducted by an upper node of the base station as necessary.

In other words, it will be obvious to those skilled in the art that various operations for enabling the base station to communicate with the terminal in a network composed of several network nodes including the base station will be conducted by the base station or other network nodes other than the base station. The term “Base Station (BS)” may be replaced with a fixed station, Node-B, eNode-B (eNB), or an access point as necessary. The term “relay” may be replaced with the terms Relay Node (RN) or Relay Station (RS). The term “terminal” may also be replaced with a User Equipment (UE), a Mobile Station (MS), a Mobile Subscriber Station (MSS) or a Subscriber Station (SS) as necessary.

It should be noted that specific terms disclosed in the present invention are proposed for convenience of description and better understanding of the present invention, and the use of these specific terms may be changed to other formats within the technical scope or spirit of the present invention.

In some instances, well-known structures and devices are omitted in order to avoid obscuring the concepts of the present invention and important functions of the structures and devices are shown in block diagram form. The same reference numbers will be used throughout the drawings to refer to the same or like parts.

Exemplary embodiments of the present invention are supported by standard documents disclosed for at least one of wireless access systems including an Institute of Electrical and Electronics Engineers (IEEE) 802 system, a 3^(rd) Generation Partnership Project (3GPP) system, a 3GPP Long Term Evolution (LTE) system, an LTE-Advanced (LTE-A) system, and a 3GPP2 system. In particular, steps or parts, which are not described to clearly reveal the technical idea of the present invention, in the embodiments of the present invention may be supported by the above documents. All terminology used herein may be supported by at least one of the above-mentioned documents.

The following embodiments of the present invention can be applied to a variety of wireless access technologies, for example, CDMA (Code Division Multiple Access), FDMA (Frequency Division Multiple Access), TDMA (Time Division Multiple Access), OFDMA (Orthogonal Frequency Division Multiple Access), SC-FDMA (Single Carrier Frequency Division Multiple Access), and the like. CDMA may be embodied through wireless (or radio) technology such as UTRA (Universal Terrestrial Radio Access) or CDMA2000. TDMA may be embodied through wireless (or radio) technology such as GSM (Global System for Mobile communication)/GPRS (General Packet Radio Service)/EDGE (Enhanced Data Rates for GSM Evolution). OFDMA may be embodied through wireless (or radio) technology such as Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, and E-UTRA (Evolved UTRA). UTRA is a part of UMTS (Universal Mobile Telecommunications System). 3GPP (3rd Generation Partnership Project) LTE (long term evolution) is a part of E-UMTS (Evolved UMTS), which uses E-UTRA. 3GPP LTE employs OFDMA in downlink and employs SC-FDMA in uplink. LTE-Advanced (LTE-A) is an evolved version of 3GPP LTE. WiMAX can be explained by IEEE 802.16e (WirelessMAN-OFDMA Reference System) and advanced IEEE 802.16m (WirelessMAN-OFDMA Advanced System). For clarity, the following description focuses on IEEE 802.11 systems. However, technical features of the present invention are not limited thereto.

FIG. 1 exemplarily shows a radio frame structure for use in the LTE system. Referring to FIG. 1(a), a radio frame includes 10 subframes, and one subframe includes two slots in the time domain. A time required for transmitting one subframe is defined as a Transmission Time Interval (TTI). For example, one subframe may have a length of 1 ms and one slot may have a length of 0.5 ms. One slot may include a plurality of OFDM symbols in time domain. Since the LTE system uses OFDMA in downlink, the OFDM symbol indicates one symbol duration. One OFDM symbol may be called an SC-FDMA symbol or a symbol duration. An RB is a resource allocation unit and includes a plurality of contiguous subcarriers in one slot. The structure of the radio frame is only exemplary. Accordingly, the number of subframes included in one radio frame, the number of slots included in one subframe, or the number of OFDM symbols included in one slot may be changed in various manners.

The structure of a type 2 radio frame is shown in FIG. 1(b). The type 2 radio frame includes two half-frames, each of which is made up of five subframes, a downlink pilot time slot (DwPTS), a guard period (GP), and an uplink pilot time slot (UpPTS), in which one subframe consists of two slots. That is, one subframe is composed of two slots irrespective of the radio frame type. DwPTS is used to perform initial cell search, synchronization, or channel estimation. UpPTS is used to perform channel estimation of a base station and uplink transmission synchronization of a user equipment (UE). The guard interval (GP) is located between an uplink and a downlink so as to remove interference generated in the uplink due to multi-path delay of a downlink signal.

The structure of the radio frame is only exemplary. Accordingly, the number of subframes included in the radio frame, the number of slots included in the subframe or the number of symbols included in the slot may be changed in various manners.

FIG. 2 is a diagram showing a resource grid in a downlink slot. Although one downlink slot includes seven OFDM symbols in a time domain and one RB includes 12 subcarriers in a frequency domain in the figure, the scope or spirit of the present invention is not limited thereto. For example, in case of a normal Cyclic Prefix (CP), one slot includes 7 OFDM symbols. However, in case of an extended CP, one slot may include 6 OFDM symbols. Each element on the resource grid is referred to as a resource element. One RB includes 12×7 resource elements. The number N^(DL) of RBs included in the downlink slot is determined based on downlink transmission bandwidth. The structure of the uplink slot may be equal to the structure of the downlink slot.

FIG. 3 is a diagram showing the structure of a downlink subframe. A maximum of three OFDM symbols of a front portion of a first slot within one subframe corresponds to a control region to which a control channel is allocated. The remaining OFDM symbols correspond to a data region to which a Physical Downlink Shared Channel (PDSCH) is allocated. The basic unit of transmission becomes one subframe. Examples of the downlink control channels used in the 3GPP LTE system include, for example, a Physical Control Format Indicator Channel (PCFICH), a Physical Downlink Control Channel (PDCCH), a Physical Hybrid automatic repeat request Indicator Channel (PHICH), etc.

PCFICH is transmitted at a first OFDM symbol of a subframe, and includes information about the number of OFDM symbols used to transmit the control channel in the subframe.

PHICH includes a HARQ ACK/NACK signal as a response to uplink transmission.

The control information transmitted through the PDCCH is referred to as Downlink Control Information (DCI). The DCI includes uplink or downlink scheduling information or an uplink transmit power control command for a certain UE group. The PDCCH may include resource allocation and transmission format of a Downlink Shared Channel (DL-SCH), resource allocation information of an Uplink Shared Channel (UL-SCH), paging information of a Paging Channel (PCH), system information on the DL-SCH, resource allocation of a higher layer control message such as a Random Access Response (RAR) transmitted on the PDSCH, a set of transmit power control commands for individual UEs in a certain UE group, transmit power control information, activation of Voice over IP (VoIP), etc. A plurality of PDCCHs may be transmitted within the control region. The UE may monitor the plurality of PDCCHs. PDCCHs are transmitted as an aggregate of one or several contiguous control channel elements (CCEs). The CCE is a logical allocation unit used to provide the PDCCHs at a coding rate based on the state of a radio channel. The CCE corresponds to a plurality of resource element groups. The format of the PDCCH and the number of available bits are determined based on a correlation between the number of CCEs and the coding rate provided by the CCEs. The eNB (or base station) determines a PDCCH format according to a DCI to be transmitted to the UE, and attaches a Cyclic Redundancy Check (CRC) to control information. The CRC is masked with a Radio Network Temporary Identifier (RNTI) according to an owner or usage of the PDCCH. If the PDCCH is for a specific UE, a cell-RNTI (C-RNTI) of the UE may be masked to the CRC. Alternatively, if the PDCCH is for a paging message, a paging indicator identifier P-RNTI) may be masked to the CRC. If the PDCCH is for system information (more specifically, a system information block (SIB)), a system information identifier and a system information RNTI (SI-RNTI) may be masked to the CRC. To indicate a random access response that is a response for transmission of a random access preamble of the UE, a random access-RNTI (RA-RNTI) may be masked to the CRC.

FIG. 4 is a diagram showing the structure of an uplink frame. The uplink subframe may be divided into a control region and a data region in a frequency domain. A Physical Uplink Control Channel (PUCCH) including uplink control information is allocated to the control region. A Physical Uplink Shared Channel (PUSCH) including user data is allocated to the data region. In order to maintain single carrier characteristics, one UE does not simultaneously transmit the PUCCH and the PUSCH. The PUCCH for one UE is allocated to an RB pair in a subframe. RBs belonging to the RB pair occupy different subcarriers with respect to two slots. Thus, the RB pair allocated to the PUCCH is “frequency-hopped” at a slot edge.

DCI Format

DCI formats 0, 1, 1A, 1B, 1C, 1D, 2, 2A, 2B, 2C, 3, 3A and 4 are defined in LTE-A (release 10). DCI formats 0, 1A, 3 and 3A have the same message size to reduce the number of blind decoding operations, which will be described later. The DCI formats may be divided into i) DCI formats 0 and 4 used for uplink scheduling grant, ii) DCI formats 1, 1A, 1B, 1C, 2, 2A, 2B and 2C used for downlink scheduling allocation, and iii) DCI formats 3 and 3A for power control commands according to purpose of control information to be transmitted.

DCI format 0 used for uplink scheduling grant may include a carrier indicator necessary for carrier aggregation which will be described later, an offset (flag for format 0/format 1A differentiation) used to differentiate DCI formats 0 and 1A from each other, a frequency hopping flag that indicates whether frequency hopping is used for uplink PUSCH transmission, information about resource block assignment, used for a UE to transmit a PUSCH, a modulation and coding scheme, a new data indicator used to empty a buffer for initial transmission with respect to an HARQ process, a transmit power control (TPC) command for a scheduled PUSCH, information on a cyclic shift for a demodulation reference signal (DMRS) and OCC index, and an uplink index and channel quality indicator request necessary for a TDD operation, etc. DCI format 0 does not include a redundancy version, differently from DCI formats relating to downlink scheduling allocation, because DCI format 0 uses synchronous HARQ. The carrier offset is not included in DCI formats when cross-carrier scheduling is not used.

DCI format 4 is newly added to DCI formats in LTE-A release 10 and supports application of spatial multiplexing to uplink transmission in LTE-A. DCI format 4 has a larger message size because it further includes information for spatial multiplexing. DCI format 4 includes additional control information in addition to control information included in DCI format 0. DCI format 4 includes information on a modulation and coding scheme for the second transmission block, precoding information for multi-antenna transmission, and sounding reference signal (SRS) request information. DCI format 4 does not include the offset for format 0/format 1A differentiation because it has a size larger than DCI format 0.

DCI formats 1, 1A, 1B, 1C, 1D, 2, 2A, 2B and 2C for downlink scheduling allocation may be divided into DCI formats 1, 1A, 1B, 1C and 1D that do not support spatial multiplexing and DCI formats 2, 2A, 2B and 2C that support spatial multiplexing.

DCI format 1C supports only frequency contiguous allocation as compact frequency allocation and does not include the carrier indicator and redundancy version, compared to other formats.

DCI format 1A is for downlink scheduling and random access procedure. DCI format 1A may include a carrier indicator, an indicator that indicates whether downlink distributed transmission is used, PDSCH resource allocation information, a modulation and coding scheme, a redundancy version, a HARQ processor number for indicating a processor used for soft combining, a new data indicator used to empty a buffer for initial transmission with respect to a HARQ process, a TPC command for a PUCCH, an uplink index necessary for a TDD operation, etc.

DCI format 1 includes control information similar to that of DCI format 1A. DCI format 1 supports non-contiguous resource allocation whereas DCI format 1A supports contiguous resource allocation. Accordingly, DCI format 1 further includes a resource allocation header, and thus slightly increases control signaling overhead as a trade-off for an increase in resource allocation flexibility.

Both DCI formats 1B and 1D further include precoding information, compared to DCI format 1. DCI format 1B includes PMI acknowledgement and DCI format 1D includes downlink power offset information. Most control information included in DCI formats 1B and 1D corresponds to that of DCI format 1A.

DCI formats 2, 2A, 2B and 2C include most control information included in DCI format 1A and further include information for spatial multiplexing. The information for spatial multiplexing includes a modulation and coding scheme for the second transmission block, a new data indicator, and a redundancy version.

DCI format 2 supports closed loop spatial multiplexing and DCI format 2A supports open loop spatial multiplexing. Both DCI formats 2 and 2A include precoding information. DCI format 2B supports dual layer spatial multiplexing combined with beamforming and further includes cyclic shift information for a DMRS. DCI format 2C may be regarded as an extended version of DCI format 2B and supports spatial multiplexing for up to 8 layers.

DCI formats 3 and 3A may be used to complement the TPC information included in the aforementioned DCI formats for uplink scheduling grant and downlink scheduling allocation, that is, to support semi-persistent scheduling. A 1-bit command is used per UE in the case of DCI format 3 whereas a 2-bit command is used per UE in the case of DCI format 3A.

One of the above-mentioned DCI formats is transmitted through a PDCCH, and a plurality of PDCCHs may be transmitted in a control region. A UE can monitor the plurality of PDCCHs.

Downlink Control Channel Structure

The first three OFDM symbols for each subframe can be basically used as a transmission region of a downlink control channel, and the first to third OFDM symbols may be used according to overhead of a downlink control channel. PCFICH may be used to adjust the number of OFDM symbols for a downlink control channel per subframe. In order to provide acknowledgement/negative acknowledgment (ACK/NACK) information for uplink transmission on downlink, a Physical Hybrid-automatic repeat request (ARQ) Indicator Channel (PHICH) may be used. In addition, a PDCCH may be used to transmit either control information for downlink data transmission or control information for uplink data transmission.

FIGS. 5 and 6 exemplarily show that the above-mentioned downlink control channels are allocated in units of a resource element group (REG) in a control region for each subframe. In more detail, FIG. 5 shows a system having 1Tx antenna or 2Tx antennas, and FIG. 6 shows a system having 4Tx antennas. As can be seen from FIGS. 5 and 6, an REG serving as a basic resource unit to which a control channel is allocated is composed of 4 concatenated resource elements (REs) in a frequency domain other than some REs to which reference signals are allocated. A predetermined number of REGs may be used to transmit a downlink control channel according to downlink control channel (DCH) overhead.

PCFICH (Physical Control Format Indicator Channel)

In order to provide resource allocation information or the like of the corresponding subframe to each subframe, a PDCCH may be transmitted among OFDM symbol indices #0 to #2. In accordance with overhead of a control channel, an OFDM symbol index #0 may be used, OFDM symbol indices #0 and #1 may be used, or OFDM symbol indices #0 to #2 may be used. The number of OFDM symbols used by a control channel may be changed per subframe, and information regarding the number of OFDM symbols may be provided over a PCFICH. Therefore, PCFICH must be transmitted per subframe.

Three kinds of information can be provided through a PCFICH. The following Table 1 shows a Control Format Indicator of a PCFICH. CFI=1 denotes that a PDCCH is transmitted at OFDM symbol index #0, CFI=2 denotes that a PDCCH is transmitted at OFDM symbol indices #0 and #1, and CFI=3 denotes that a PDCCH is transmitted at OFDM symbol indices #0 to #2.

TABLE 1 CFI CFI codeword <b₀, b₁, . . . , b₃₁> 1 <0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1> 2 <1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0> 3 <1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1> 4 <0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0> (Reserved)

Information transmitted over a PCFICH may be differently defined according to system bandwidth. For example, if a system bandwidth is less than a specific threshold value, CFI=1, CFI=2, and CFI=3 may indicate that two OFDM symbols, three OFDM symbols, and four OFDM symbols are used for a PDCCH, respectively.

FIG. 7 is a conceptual diagram illustrating a PCFICH transmission scheme. An REG shown in FIG. 7 may be composed of 4 subcarriers, and may be composed only of data subcarriers other than a reference signal (RS). Generally, a transmit diversity scheme may be applied to the REG. To prevent inter-cell interference of the PCFICH, the REGs to which the PCFICH is mapped may be shifted per cell in the frequency domain (according to a cell ID). The PCFICH is transmitted at the first OFDM symbol of a subframe all the time. Accordingly, when receiving a subframe, the receiver first confirms PCFICH information, and recognizes the number of OFDM symbols needed for PDCCH transmission, such that it can receive control information transmitted over a PDCCH.

Physical Hybrid-ARQ Indicator Channel (PHICH)

FIG. 8 shows the positions of PCFICH and PHICH generally applied to a specific bandwidth. ACK/NACK information for uplink data transmission is transmitted over a PHICH. A plurality of PHICH groups is constructed in a single subframe, and a plurality of PHICHs may be present in a single PHICH group. Therefore, PHICH channels for multiple UEs are contained in a single PHICH group.

Referring to FIG. 8, allocating a PHICH to each UE of a plurality of PHICH groups is achieved not only using a lowest physical resource block (PRB) index of a PUSCH resource allocation but also a cyclic shift (CS) index for a demodulation RS (DMRS) transmitted on a UL grant PDCCH. DMRS is an uplink reference signal, and is provided along with UL transmission so as to perform channel estimation for demodulating UL data. In addition, a PHICH resource is signaled as an index pair such as (n_(PHICH) ^(group), n_(PHICH) ^(seq)). In the index pair (n_(PHICH) ^(group), n_(PHICH) ^(seq)), n_(PHICH) ^(group) denotes a PHICH group number and n_(PHICH) ^(seq) denotes an orthogonal sequence index in the corresponding PHICH group. n_(PHICH) ^(group) and n_(PHICH) ^(seq) are defined as shown in the following equation 1. n _(PHICH) ^(group)=(I _(PRB) _(_) _(RA) ^(lowest) ^(_) ^(index) +n _(DMRS))mod N _(PHICH) ^(group) n _(PHICH) ^(seq)=(└I _(PRB) _(_) _(RA) ^(lowest) ^(_) ^(index) /N _(PHICH) ^(group) ┘+n _(DMRS))mod 2N _(SF) ^(PHICH)  [Equation 1]

In Equation 1, n_(DMRS) denotes a cyclic shift of a DMRS used for uplink transmission related to a PHICH, and is mapped to a value of ‘cycle shift for DMRS’ field of the latest UL grant control information (e.g., DCI format 0 or 4) for a transport block (TB) associated with the corresponding PUSCH transmission. For example, the ‘cyclic shift for DMRS’ field of the latest UL grant DCI format may be 3 bits long. If the ‘cyclic shift for DMRS’ field is set to “000”, n_(DMRS) may be set to zero ‘0’.

In Equation 1, N_(SF) ^(PHICH) denotes the size of a spreading factor used for PHICH modulation. I_(PRB) _(_) _(RA) ^(lowest) ^(_) ^(index) is the lowest PRB index of a first slot of the corresponding PUSCH transmission. I_(PHICH) is set to the value of 1 only when the TDD system is in a special case (if UL/DL configuration is set to zero ‘0’ and PUSCH transmission is achieved at subframe n=4 or n=9, and I_(PHICH) is set to zero ‘0’ in the remaining cases other than the special case. N_(PHICH) ^(group) denotes the number of PHICH groups configured by a higher layer. N_(PHICH) ^(group) can be obtained using the following equation 2.

$\begin{matrix} {N_{PHICH}^{group} = \left\{ \begin{matrix} \left\lceil {N_{g}\left( {N_{RB}^{DL}/8} \right)} \right\rceil & {{for}\mspace{14mu}{normal}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}} \\ {2 \cdot \left\lceil {N_{g}\left( {N_{RB}^{DL}/8} \right)} \right\rceil} & {{for}\mspace{14mu}{extended}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}} \end{matrix} \right.} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack \end{matrix}$

In Equation 2, N_(g) denotes information regarding the amount of PHICH resources transmitted on a physical broadcast channel (PBCH), and N_(g) is 2 bits long and is denoted by N_(g) ε{⅙, ½, 1, 2}. In Equation 2, N_(RB) ^(DL) denotes the number of resource blocks (RBs) configured in downlink.

In addition, examples of orthogonal sequences defined in the legacy 3GPP LTE Release 8/9 are shown in the following table 2.

TABLE 2 Sequence Orthogonal sequence index Normal cyclic prefix Extended cyclic prefix n_(PHICH) ^(seq) N_(SF) ^(PHICH) = 4 N_(SF) ^(PHICH) = 2 0 [+1 +1 +1 +1] [+1 +1] 1 [+1 −1 +1 −1] [+1 −1] 2 [+1 +1 −1 −1] [+j +j] 3 [+1 −1 −1 +1] [+j −j] 4 [+j +j +j +j] — 5 [+j −j +j −j] — 6 [+j +j −j −j] — 7 [+j −j −j +j] —

FIG. 9 shows a downlink resource element position mapped to a PHICH group. A PHICH group may be constructed in different time domains (i.e., different OFDM Symbols (OSs)) of a single subframe shown in FIG. 9 according to PHICH duration.

PDCCH Processing

When PDCCHs are mapped to REs, control channel elements (CCEs) corresponding to contiguous logical allocation units are used. A CCE includes a plurality of (e.g. 9) REGs and an REG includes 4 neighboring REs except for a reference signal (RS).

The number of CCEs necessary for a specific PDCCH depends on a DCI payload corresponding to control information size, cell bandwidth, channel coding rate, etc. Specifically, the number of CCEs for a specific PDCCH can be determined based on PDCCH format shown in Table 3.

TABLE 3 Number Number Number of PDCCH of of PDCCH format CCEs REGs bits 0 1 9 72 1 2 18 144 2 4 36 288 3 8 72 576

While one of the above-mentioned four PDCCH formats may be used, this is not signaled to a UE. Accordingly, the UE performs decoding without knowing the PDCCH format, which is referred to as blind decoding. Since operation overhead is generated if a UE decodes all CCEs that can be used for downlink for each PDCCH, a search space is defined in consideration of limitation for a scheduler and the number of decoding attempts.

The search space is a set of candidate PDCCHs composed of CCEs on which a UE needs to attempt to perform decoding at an aggregation level. The aggregation level and the number of candidate PDCCHs can be defined as shown in Table 4.

TABLE 4 Search space The number of Aggregation Size PDCCH level (CCE unit) candidates UE-specific 1 6 6 2 12 6 4 8 2 8 16 2 Common 4 16 4 8 16 2

As shown in Table 4, the UE has a plurality of search spaces at each aggregation level because 4 aggregation levels are present. The search spaces may be divided into a UE-specific search space and a common search space, as shown in Table 4. The UE-specific search space is for a specific UE. Each UE may check an RNTI and CRC which mask a PDCCH by monitoring a UE-specific search space thereof (attempting to decode a PDCCH candidate set according to an available DCI format) and acquire control information when the RNTI and CRC are valid.

The common search space is used for a case in which a plurality of UEs or all UEs need to receive PDCCHs, for system information dynamic scheduling or paging messages, for example. The common search space may be used for a specific UE for resource management. Furthermore, the common search space may overlap with the UE-specific search space.

The search space may be decided by the following equation 3. L·{(Y _(k) +m′)mod└N _(CCE,k) /L┘}+i  [Equation 3]

In Equation 3, L is an aggregation level, Y_(k) is a variable decided by RNTI and subframe number (k), m′ is the number of PDCCH candidates. If carrier aggregation (CA) is used, m′ is denoted by m′=m+M^((L))·n_(CI). If CA is not used, m′ is denoted by m′=m, where m=0, . . . , M^((L))−1. M^((L)) is the number of PDCCH candidates. N_(CCE,k) is a total number of CCEs of a control region at the k-th subframe. i is an index for determination of a separate CCE in each PDCCH candidate in the PDCCH and satisfies i=0, . . . , L−1. In a common search space, Y_(k) is always set to zero ‘0’.

FIG. 10 is a conceptual diagram illustrating a UE-specific search space (shaded part) in each aggregation level defined by Equation 3. In FIG. 10, it should be noted that carrier aggregation (CA) is not used and the number of N_(CCE,k) is exemplarily set to 32.

FIGS. 10(a), 10(b), 10(c), and 10(d) show a case of an aggregation level ‘1’, a case of an aggregation level ‘2’, a case of an aggregation level ‘4’, and a case of an aggregation level ‘8’, respectively. In FIG. 10, a start CCE of a search space in each aggregation level is determined to be an RNTI and subframe number (k), and may have different values according to individual aggregation levels due to a modulo function and an aggregation level (L) within the same subframe for one UE. The start CCE may always be set only to a multiple of an aggregation level due to the aggregation level (L). In this case, it is premised that Y_(k) is set to, for example, a CCE number #18. The UE attempts to sequentially perform decoding from the beginning of a start CCE in units of CCEs decided by the corresponding aggregation level. For example, as can be seen from FIG. 10(b), the UE attempts to perform decoding on the basis of two CCEs according to an aggregation level from the beginning of a CCE number #4 acting as a start CCE.

The UE attempts to decode a search space, as described above. The number of decoding attempts is determined by DCI format and transmission mode determined through RRC signaling. When carrier aggregation (CA) is not applied, the UE needs to perform a maximum of 12 decoding attempts because 2 DCI sizes (DCI format 0/1A/3/3A and DCI format 1C) have to be considered for each of 6 PDCCH candidates for a common search space. For a UE-specific search space, 2 DCI sizes are considered for (6+6+2+2=16) PDCCH candidates and thus a maximum of 32 decoding attempts is needed. Accordingly, a maximum of 44 decoding attempts needs to be performed when carrier aggregation (CA) is not applied.

On the other hand, if carrier aggregation (CA) is used, as many UE-specific search space as the number of DL resources (component carriers: CCs) and a decoding process for DCI format 4 are further added, such that a maximum number of decoding times can be increased.

All UEs for use in the above-mentioned legacy LTE/LTE-A system have disclosed DCI on the basis of PDCCH transmitted on resources indicated by PCFICH, a method for allocating a new structure and a new PDCCH operating in a transmission mode to a PDSCH region in consideration of not only various cell deployment scenarios such as RRH (Remote Radio Head) but also MIMO (Multiple Input Multiple Output) such as feedback-based closed-loop beamforming of a UE has been intensively discussed in LTE Release 11 and up. A newly defined PDCCH will hereinafter be referred to as E-PDCCH, and a conventional PDCCH will hereinafter be referred to as a legacy PDCCH.

The legacy UEs perform blind decoding for DCI format configured by higher layer signaling on the basis of a control channel transmission (Tx) unit having a single structure in the legacy PDCCH region. However, when receiving DCI through E-PDCCH, the Tx mode and structure of E-PDCCH may be changed according to channel characteristics of the corresponding UE. In addition, from the viewpoint of one UE, the UE has to perform blind decoding not only for DCI format configured through higher layer signaling but also for DCI formats 1A/0 configured to operate in a fallback mode. In this case, during transmission of DCI format configured through higher layer signaling, not only the E-PDCCH transmission structure and mode, but also the E-PDCCH transmission structure and mode for a fallback DCI format need to be changed within the same USS. Accordingly, a method for performing blind decoding by a UE so as to support the above requirements will hereinafter be described in detail.

Embodiment 1

Embodiment 1 relates to a method for enabling a UE to decide a resource region to be used as a target of blind decoding such that the target resource region is dependently decided according to a Tx mode or DCI format. The Tx mode and associated DCI format will hereinafter be described in detail.

The BS (or eNB) may configure the Tx mode according to a channel status associated with the UE through UE-specific higher layer signaling. In addition, DCI format is decided according to the Tx mode such that the corresponding UE can perform blind decoding in a UE-specific search space and a common search space (CSS) according to the Tx mode. The following Table 5 shows this relationship.

TABLE 5 Transmission Transmission scheme of PDSCH (Tx) mode (DCI format Search Space corresponding to PDCCH Mode 1 1A Common search Single antenna port, Port 0 space (CSS) and UE- specific search space (Common and UE specific by C-RNTI) 1 UE-specific search Single antenna port, Port 0 space (UE specific by C-RNTI) Mode 2 1A Common search Transmit diversity space (CSS) and UE- specific search space 1 UE-specific search Transmit diversity space Mode 3 1A Common search Transmit diversity space (CSS) and UE- specific search space 2A UE-specific search Large delay cyclic delay diversity space (CDD) or Tx diversity Mode 4 1A Common search Transmit diversity space (CSS) and UE- specific search space 2 UE-specific search Closed Loop Spatial Multiplexing or space Closed Loop Spatial Multiplexing or Transmit Diversity Mode 5 1A Common search Transmit diversity space (CSS) and UE- specific search space 1D UE-specific search Multi-user MIMO space Mode 6 1A Common search Transmit diversity space (CSS) and UE- specific search space 1B UE-specific search Closed Loop Spatial Multiplexing using space single layer Mode 7 1A Common search If one PBCH antenna port is present, space (CSS) and UE- Port #0 is used, and the remaining ports specific search space other than Port #0 correspond to Tx diversity. 1 UE-specific search Single Antenna Port, Port 5 space Mode 8 1A Common search If one PBCH antenna port is present, space (CSS) and UE- Port #0 is used, and the remaining ports specific search space other than Port #0 correspond to Tx diversity 2B UE-specific search Dual-layer transmission of Antenna Ports #7 space and #8 or Single Antenna Port of Antenna port #7 or #8 Mode 9 1A Common search If MBSFN subframe is not decided, this space (CSS) and UE- means that one PBCH antenna port is present specific search space and Port #0 is used. In the remaining cases other than this case, Tx diversity is decided. If MBSFN subframe is decided, this means that single antenna port is used and Port #7 is used. 2C UE-specific search 8-Layer Transmission—Use of Ports 7-14 space or Single Antenna Port of Antenna Port #7 or #8

In Table 5, for example, in case of a transmission (Tx) mode #9, the UE performs blind decoding for DCI format 1A in a common search space (CSS) for cell-specific control information. For UE-specific control information, the UE performs blind decoding not only for DCI format 1A but also for DCI format 2C indicated by higher layer signaling indicated by higher layer signaling. For details of Table 5, reference is made to 3GPP TS 36.213, etc.

Table 5 is used in the legacy LTE/LTE-A system. A resource region for DCI transmission corresponds to first three or four OFDM symbols of the subframe indicated by PCFICH. If the above-mentioned E-PDCCH is transmitted to the PDSCH region, a resource region in which the UE has to perform blind decoding according to the Tx mode or DCI format may be changed. In more detail, beamforming or the like is applied to a specific transmission mode (e.g., Tx mode 8 or 9), such that it is preferable that E-PDCCH be transmitted to contiguous resource regions. Alternatively, E-PDCCH may be transmitted to a distributed resource region in other Tx mode (e.g., Tx modes 1˜7). In addition, even in the case of a specific Tx mode (e.g., Tx mode 8 or 9), fallback DCI (for example, DCI format 1A) may be transmitted to the distributed resource region. In case of DCI format (e.g., in case of Tx mode 8, DCI format 2B; and in case of Tx mode 9, DCI format 2C) associated with PDSCH transmission based on a plurality of layers, E-PDCCH may be transmitted to contiguous resource regions.

Accordingly, when the UE performs blind decoding, blind decoding may be performed in the distributed E-PDCCH resource region according to Tx mode, or blind decoding may be performed in the contiguous E-PDCCH resource region. In addition, during blind decoding for a fallback DCI format even in the same Tx mode, the blind decoding can be performed in the contiguous resource region. In case of blind decoding for DCI format (for example, DCI formats 2B, 2C, etc.) indicated by higher layer signaling, blind decoding may be performed in the contiguous resource region.

A detailed description thereof will hereinafter be described with reference to FIG. 11.

The type-1 CCE structure is shown in FIG. 11(a). The type-2 CCE structures shown in FIG. 11(b). In this case, the type-1 CCE structure and the type-2 CCE structure exemplarily show an E-PDCCH resource region of the contiguous resource block (RB) and an E-PDCCH resource region of the distributed resource block (RB). The term “CCE” means a resource region, and may be replaced with another term “RB” or the like without departing from the scope or spirit of the present invention.

The UE performs blind decoding for a resource region used for E-PDCCH transmission, and may receive a plurality of first indexes contiguous to each other so as to implement blind decoding. In this case, each of the first indexes may be one resource block (RB) or a resource region corresponding to the number of REs (or half number of REs) contained in one CCE. From the plurality of first indexes, a second index for indicating the distribute resource region can be decided as shown in FIG. 11(a) or FIG. 11(b).

In more detail, for example, a plurality of first indexes contiguous to each other may be indexes #0 to #7, and individual first indexes may sequentially indicate specific resource regions (1100˜4107) as shown in FIG. 11(a). In this case, the second index is decided (mapped) in the same manner as in the first index such that contiguous resource regions can be indicated as shown in FIG. 11(a), and a CCE can be sequentially decided on the contiguous resource region. The UE may perform blind decoding per aggregation level using the CCE of the above-mentioned decided contiguous resource region.

A plurality of second indexes may be decided to indicate the distributed resource region from the first indexes contiguous to each other. In other words, the second indexes may be rearranged in a manner that the resource regions indicated by the first indexes are distributed on a frequency axis. For example, a plurality of second indexes may be decided to be 0, 2, 4, 6, 1, 3, 5, 7 on the basis of the first indexes (0, 1, 2, 3, 4, 5, 6, 7). CCE may be decided in order of a resource region indicated by the second index. In other words, as show in FIG. 11(b), if the first indexes (0, 1, 2, 3, 4, 5, 6, 7) respectively indicate specific resource regions (a, b, c, d, e, f, g, h), the second indexes enables the specific resource regions (a, b, c, d, e, f, g, h) to respectively indicate (0, 2, 4, 6, 1, 3, 5, 7). CCE is sequentially decided in the resource region indicated by the order of second indexes, such that CCE may be determined within the resource region sequentially indicated in the order of resource regions (a, e, b, f, c, g, d, h). Specifically, since a specific resource region indicated any one of the first index and the second index shown in FIG. 11(b) includes 16 REs other than reference signals (RSs), two specific resource regions comprise one CCE. As a result, according to the order of second indexes, the resource regions (a, e) may correspond to CCEs #0, b, f, the resource regions (b, f) may correspond to CCE #1, the resource regions (c, g) may correspond to CCE #2, and the resource regions (d, h) may correspond to CCE #3. However, deciding the second index from the first index shown in FIG. 11(b) is only exemplary, and other patterns indicating the distributed resources may be applied.

As described above, deciding the second index from the first index may indicate the contiguous resource region or the distributed resource region, and deciding a plurality of second indexes may be dependent upon at least one of the Tx mode and the DCI format. In more detail, for example, in case of a Tx mode #8 or #9 associated with data transmission based on a plurality of layers, the second indexes may equally decide the first indexes so as to indicate the contiguous resource region as shown in FIG. 11(a). In case of other Tx modes other than the Tx modes #8 and #9 shown in FIG. 11(a), the plurality of second indexes may be decided in a manner that the resource regions indicated by individual first indexes can be distributed on the frequency axis as shown in FIG. 11(b).

In case of Tx mode #8 or #9, deciding the second indexes according to DCI format may indicate the distributed resource region or the contiguous resource region. In more detail, referring back to Table 5, in case of Tx modes #8 and #9, blind decoding is performed for DCI format 1A corresponding to a fallback DCI format within the UE-specific search space and the common search space (CSS). In case of DCI format 1A, the resource region in which decision of the second index is distributed can be indicated as described above. If blind decoding is performed not only for DCI format 2B in Tx mode #8 but also for DCI format 2C (i.e., DCI format related to PDSCH transmission based on DMRS) in Tx mode #9, the UE may decide the distributed resource region to indicate the distributed second index.

As described above, specific information as to which scheme will be used for decision of the second index and a relationship between Tx mode and/or DCI format may be preconfigured. The specific information and the relationship may be semi-statically decided through higher layer signaling, or may be dynamically transmitted through the legacy PDCCH/E-PDCCH, etc. Alternatively, the above relationship may be configured as a mapping table.

Embodiment 2

The contiguous resource region and the distributed resource region may be pre-constructed on a single subframe as shown in FIG. 12. Specific information as to whether blind decoding will be performed on the contiguous resource region or the distributed resource region according to Tx mode and/or DCI format will be decided. For example, for DCI format 2B, the UE configured in Tx mode #8 may perform blind decoding in the contiguous resource region (Type-1 USS) as shown in FIG. 12. For DCI format 1A, the UE may perform blind decoding in the distributed resource region (Type-1 USS) shown in FIG. 12. Likewise, for DCI format 2C, the UE configured in Tx mode #9 may perform blind decoding in the contiguous resource region. For DCI format 1A, the UE may perform blind decoding in the distributed resource region (Type-1 USS).

In accordance with the above-mentioned embodiments, allocation information of the resource region may be decided by UE-specific higher layer signaling, a C-RNTI function, etc. For example, allocation of the resource region by a UE identifier (ID) may use a hash function for deciding the UE-specific search space in the legacy LTE/LTE-A system. Similarly to the scheme for deciding a search space using Equation 3, the resource-region allocation information may also be decided by the following equation 4. In this case, in the k-th subframe, a total number N_(CCE,k) of CCEs of the control region may be replaced with a total number N_(RB) of RBs of a downlink bandwidth. (Z _(k) ^((L)) +i)mod N _(CCE,k), (i=0,1, . . . , M ^((L)) ·L−1)  [Equation 4]

where Z_(k) ^((L)) denotes a start position of the search space, and is decided by the following equation, Z _(k) ^((L)) =L·(Y _(k) mod└N _(CCE,k) /L┘) Y _(k)=(A·Y _(k-1))mod D (Y ⁻¹ =n _(RNTI)≠0,A=39827,D=65537.)

where M^((L)) denotes the number of PDCCH candidates.

In addition, the type-1 CCE structure and the type-2 CCE structure may be changed according to the multiplexing schemes (FDM, TDM/FDM) of E-PDCC and PDSCH, the number of cell-specific CRS ports, the number of DMRS ports, etc. In addition, the type-2 CCE structure may be changed according to the interleaving scheme on the frequency axis. For example, in addition to the example of FIG. 11(b), the interleaving scheme may be used on an REG basis. In addition, new two or more types of CCE structures may be defined, the CCE structure mapping table per DCI format or the CCE structure mapping table per Tx mode are configured, and the case of performing blind decoding in the UE-specific search space may also be contained in the scope of the present invention.

In the meantime, if E-PDCCH is transmitted in the PDSCH region as described above, the UE performs channel measurement and demodulation using a DMRS. In this case, if PDSCH allocation is achieved through the fallback DCI format (i.e., DCI format 1A), the UE has to use the cell-specific RS to demodulate the PDSCH. In other words, E-PDCCH performs demodulation on the basis of DMRS and PDSCH has to perform demodulation on the basis of the cell-specific RS, such that double burdens may be assessed on the UE. Accordingly, two methods of fallback DCI formats for a UE configured to receive E-PDCCH based on DMRS through E-PDCCH will hereinafter be described in detail.

In a first method, in case of the UE configured to receive E-PDCCH, the PDSCH transmission scheme associated with the fallback DCI format is used differently from the legacy UE. Referring back to Table 5, the PDSCH transmission scheme associated with DCI formats (for example, DCI formats 1, 1B, 1D, 2, 2A, 2B of Table 5) dependent upon each Tx mode remains unchanged, and may be changed for the UE configured to receive the PDSCH transmission scheme related to the fallback DCI format (i.e., DCI format 1A) in the case of “single antenna port transmission through Port #7”. Therefore, the PDSCH transmission scheme of Table 5 may be applied to a UE configured to receive DCI through the legacy PDCCH, and the above-mentioned changed PDSCH transmission scheme may be applied to a UE configured to receive DCI through E-PDCCH. In other words, although the same Tx mode is configured, the PDSCH transmission scheme associated with the fallback DCI may be changed according to whether a UE can receive DCI through E-PDCCH.

In a second method, a new Tx mode for a UE configured in LTE Release 11 or higher for E-PDCCH reception is defined. In more detail, one or more new Tx modes for the UE configured in Release 11 or higher are added to the Tx modes of Table 5, and the PDSCH transmission scheme associated with the fallback DCI format in a new Tx mode is configured to implement “Single Antenna Port Transmission through Port #7”. Under the above-mentioned situation, a UE of Release 11 or higher performs blind decoding in the legacy PDCCH region on the condition that the Tx mode configured for the UE is the legacy Tx modes #1 to #9. In case of a newly defined Tx mode, the UE can perform blind decoding in the E-PDCCH region.

FIG. 13 is a block diagram illustrating a BS (eNB) device and a UE device according to the embodiments of the present invention.

Referring to FIG. 13, the BS device 1310 according to the present invention may include a reception (Rx) module 1311, a transmission (Tx) module 1312, a processor 1313, a memory 1314, and a plurality of antennas 1315. The plurality of antennas 1315 indicates the BS device for supporting MIMO transmission and reception. The reception (Rx) module 1311 may receive a variety of signals, data and information on an uplink starting from the UE. The Tx module 1312 may transmit a variety of signals, data and information on a downlink for the UE. The processor 1313 may provide overall control to the BS device 1310. The processor 1313 may be configured to implement the embodiments of the present invention.

The processor 1313 of the BS device 1310 processes information received at the BS device 1410 and transmission information to be transmitted externally. The memory 1314 may store the processed information for a predetermined time. The memory 1314 may be replaced with a component such as a buffer (not shown).

Referring to FIG. 13, the UE device 1320 may include an Rx module 1321, a Tx module 1322, a processor 1323, a memory 1324, and a plurality of antennas 1325. The plurality of antennas 1325 indicates a UE device supporting MIMO transmission and reception. The Rx module 1321 may receive downlink signals, data and information from the BS (eNB). The Tx module 1322 may transmit uplink signals, data and information to the BS (eNB). The processor 1323 may provide overall control to the UE device 1320. The processor 1323 may be configured to implement the embodiments of the present invention.

The processor 1323 of the UE device 1320 processes information received at the UE device 1320 and transmission information to be transmitted externally. The memory 1324 may store the processed information for a predetermined time. The memory 1324 may be replaced with a component such as a buffer (not shown).

The specific configurations of the BS device and the UE device may be implemented such that the various embodiments of the present invention are performed independently or two or more embodiments of the present invention are performed simultaneously. Redundant matters will not be described herein for clarity.

The description of the BS device 1310 shown in FIG. 13 may be applied to the eNB (BS), or may also be applied to a relay node (RN) acting as a DL transmission entity or UL reception entity without departing from the scope or spirit of the present invention. In addition, the description of the UE device 1320 may be applied to the UE, or may also be applied to a relay node (RN) acting as a UL transmission entity or DL reception entity without departing from the scope or spirit of the present invention.

The above-described embodiments of the present invention can be implemented by a variety of means, for example, hardware, firmware, software, or a combination thereof.

In the case of implementing the present invention by hardware, the present invention can be implemented with application specific integrated circuits (ASICs), Digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), a processor, a controller, a microcontroller, a microprocessor, etc.

If operations or functions of the present invention are implemented by firmware or software, the present invention can be implemented in the form of a variety of formats, for example, modules, procedures, functions, etc. Software code may be stored in a memory to be driven by a processor. The memory may be located inside or outside of the processor, so that it can communicate with the aforementioned processor via a variety of well-known parts.

The detailed description of the exemplary embodiments of the present invention has been given to enable those skilled in the art to implement and practice the invention. Although the invention has been described with reference to the exemplary embodiments, those skilled in the art will appreciate that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention described in the appended claims. For example, those skilled in the art may use each construction described in the above embodiments in combination with each other. Accordingly, the invention should not be limited to the specific embodiments described herein, but should be accorded the broadest scope consistent with the principles and novel features disclosed herein.

Those skilled in the art will appreciate that the present invention may be carried out in other specific ways than those set forth herein without departing from the spirit and essential characteristics of the present invention. The above exemplary embodiments are therefore to be construed in all aspects as illustrative and not restrictive. The scope of the invention should be determined by the appended claims and their legal equivalents, not by the above description, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein. Also, it will be obvious to those skilled in the art that claims that are not explicitly cited in the appended claims may be presented in combination as an exemplary embodiment of the present invention or included as a new claim by subsequent amendment after the application is filed.

INDUSTRIAL APPLICABILITY

Although the embodiments of the present invention have been disclosed on the basis of the 3GPP LTE mobile communication system, the embodiments can be equally or equivalently applied to various wireless communication systems. 

The invention claimed is:
 1. A method for acquiring control information by a user equipment (UE) in a wireless communication system, comprising: receiving a plurality of first indexes which are contiguously associated with a resource region in which downlink control information (DCI) is transmitted; determining a plurality of second indexes from the plurality of first indexes; determining a control channel element (CCE) in order of resource regions dependent upon the plurality of second indexes; and performing blind decoding of the resource region for the CCE, wherein the determination of the plurality of second indexes is dependent upon at least one of a transmission (Tx) mode and a DCI format.
 2. The method according to claim 1, wherein: if the Tx mode is associated with data transmission based on a plurality of layers, and if blind decoding of the resource region is for a fallback DCI format, the second indexes are achieved by rearrangement of the first indexes in a manner that resource regions respectively indicated by the first indexes are distributed on a frequency axis.
 3. The method according to claim 2, wherein the data transmission associated with the fallback DCI format is achieved by use of a demodulation reference signal (DMRS).
 4. The method according to claim 2, wherein the fallback DCI format is DCI format 1A.
 5. The method according to claim 1, wherein: if the Tx mode is associated with data transmission based on a plurality of layers, and if blind decoding for the resource region is for a DCI format associated with data transmission based on a plurality of layers, the second indexes are identical to the first indexes.
 6. The method according to claim 5, wherein the data transmission based on the plurality of layers is achieved by use of a demodulation reference signal (DMRS).
 7. The method according to claim 5, wherein the DCI format associated with the data transmission based on the plurality of layers is any one of DCI format 2B and DCI format 2C.
 8. The method according to claim 1, wherein: if the Tx mode is not associated with data transmission for which a demodulation reference signal (DMRS) and a plurality of layers are used, the second indexes are achieved by rearrangement of the first indexes in a manner that the resource regions respectively indicated by the first indexes are distributed on a frequency axis, irrespective of the DCI format.
 9. The method according to claim 1, wherein the DCI is UE-specific control information.
 10. The method according to claim 1, wherein the resource region does not include a resource region indicated by a physical control format indicator channel (PCFICH).
 11. The method according to claim 1, wherein the resource region indicated by each of the first indexes corresponds to one resource block (RB).
 12. The method according to claim 1, wherein the resource region indicated by each of the first indexes corresponds to the number of resource elements (REs) contained in the CCE.
 13. A user equipment (UE) device for use in a wireless communication system, the UE comprising: a reception (Rx) module configured to receive a plurality of first indexes which are contiguously associated with a resource region in which downlink control information (DCI) is transmitted; and a processor operatively coupled to the Rx module and configured to: determine a plurality of second indexes from the plurality of first indexes, determine a control channel element (CCE) in order of resource regions dependent upon the plurality of second indexes, and perform blind decoding of the resource region for the CCE, wherein the determination of the plurality of second indexes is dependent upon at least one of a transmission (Tx) mode and a DCI format. 